The present invention relates to a method of calibrating probe pins which are mounted to self-centering work-contacting probe systems of multicoordinate measurement machines.
Measurement or probe systems of multicoordinate measurement machines are frequently provided with a plurality of probe pins (for example, in star-shaped probe-pin combinations), or with a rotary swing probe, and each probe pin carries a work-contact ball at its tip end. The coordinates of the center points of the balls of the individual probes, or the positions assumed by them after rotation, must be calibrated with reference to their mutual relative position if more than merely a single probe pin of the combination or more than one position of the swing probe is to be used for the measurement of the workpiece.
In the calibration process, the coordinates of the center point of each ball are determined with reference to a suitable calibration standard, for example, in the form of a cube or a ball, the same probe pin being moved into contact with the calibration standard from different sides, at least three times (cube) or four times (ball). Thus, in the case of a probe system having five probe pins, 15 to 20 probings are effected for the calibration, which is very time-consuming.
From publication S 60-21-002 d of the firm of Carl Zeiss, entitled "Mess-und Tastsysteme bei Mehrkoordinaten Messgeraeten" (Measurement and Probe Systems for Multicoordinate Measuring Instruments), it is known to use an angular probe in combination with a so-called trio of balls in order to expand the measurement range of multicoordinate measurement machines. To calibrate the probe pin in positions associated with two measurement ranges, a single probing of the ball trio is sufficient, provided that the involved probe system is of the self-centering variety. However, with this trio of balls it is not possible to simultaneously calibrate probe pins whose axial directions differ substantially from each other.